1. Field of the Invention
The invention relates to a radar system for obstacle warning and imaging the surface of the earth.
2. The Prior Art
A radar system for obstacle warning and imaging the surface of the earth is known from DE 40 07 612 C1. There, a forward-view radar is described, which is attached to the fuselage of an aircraft, and images the sector region lying ahead of the aircraft in two dimensions. In this connection, the forward-view radar described comprises an antenna consisting of several antenna elements arranged next to one another, for sending and receiving. By means of turning on and scanning the antenna elements, in a time sequence, one after the other, a synthetic aperture is generated, as it is known from the SAR principle. In this connection, the analysis of the radar signals takes place in such a manner that each antenna element is analyzed individually, whereby digital processing is carried out for each angle range, by means of correlation of a special, predetermined referenced function. A disadvantage in this connection is the poor angle resolution. Other analysis methods are known from Fan, Z. F. et al., in “High Resolution Imaging of Objects at Ka Band,” IEEE Trans. on Aerospace and Electronic Systems, 1995, Vol. 31, Issue 4, p. 1348–1352, and Li, H.-J. et al., in “Nonuniformly Spaced Array Imaging,” IEEE Trans. on Antennas and Propagation, 1993, Vol. 41, Issue 3, page 278–286.
The radar system known from DE 40 07 612 C1 proves to be disadvantageous in that it can only image the forward-lying sector region. Regions adjacent to the side must be imaged by means of additionally installed antenna systems. This means a significant installation effort and expenditure. In addition, complicated analysis methods are required in order to be able to image the various sector regions.